Divine intervention.

Sarah moved closer to Joe so that their breasts touched at the nipples. Joe's were by far the greater of the two and her nipples mashed into Sarah's breasts. The two locked eyes and drew even closer. Closing their eyes their lips touched and their tongues found one anothers and began to move of their own accord. To Joe's delight, Sarah moved her hand down over Joe's right breast, cupping it, then squeezing it. Joe's hand also wandered, but it traveled further south and rested over Sarah's hot pussy lips. Joe began to move her palm back and forth over Sarah's swollen lips, rubbing down hard over her exposed clit. She then parted Sarah's lips with two fingers and pressed her middle finger inside the moist fleshy folds of Sarah's snatch.
Sarah's kissing ended there as she let out a gasp. She stared dazedly into Joe's eyes as she rocked back and forth on her probing finger.

At that point the gym teacher Miss Bauer entered the locker room, looking for her two late students.

"Girls!" She said out-loud as she caught the two in their forbidden act.

The two girls nearly jumped out of the shower when Miss Bauer confronted them, each quickly grabbing a towel and wrapping themselves. They both searched for words as they tried to explain the situation, but nothing coherent made it's way out of their mouths. In the end Miss Bauer dismissed the situation and told the girls to hurry up.

"Oh and one more thing Miss Sarah, could you please go see Mr. John after class, as he has something important to tell you."

A smile came over Joe's face as she looked at her friend with envy. Miss Bauer looked confused over the sudden cheerfulness but then turned on her heels and marched out of the room yelling at the girls that they had just 2 minutes to get ready.

"What are you smiling at?" Sarah asked.

Joe just looked at her for a moment and then replied with a cheekish grin, "Oh you know that I can't let you go see Mr. John all alone! I am coming with you."
Sarah opened her mouth in objection but Joe had already grabbed at some clothes and was running out the door.